Discovery of dinosaurs in Morocco offers clues as to why they disappeared
Sciences et technologies

Discovery of dinosaurs in Morocco offers clues as to why they disappeared

Dinosaurs that lived in Morocco during the Cretaceous period. Source: Raoul Martin

According to Nicholas R. Longrich, senior lecturer in palaeontology and evolutionary biology and life sciences at the University of Bath, Africa’s last dinosaurs, especially the various carnivorous dinosaurs, flourished shortly before their sudden extinction. And it is in the phosphate mineral deposits of Morocco that his theory will be confirmed.

66 million years ago, the last dinosaurs disappeared from Earth. Scientists are still trying to understand why. New fossils of abelisaurs – distant relatives of tyrannosaurs – from Morocco suggest that African dinosaurs remained diverse before their extinction. And this supports the theory that their disappearance occurred suddenly, with the impact of a giant asteroid, analyzes Nicholas R. Longrich, lecturer in paleontology and evolutionary biology, life sciences at the University of Bath.

In an article published in Talk, the paleontologist recalls, the causes of this mass extinction have been the subject of debate for two centuries. Georges Cuvier, the father of paleontology, believed that catastrophes were the cause. Charles Darwin, on the other hand, believed that progressive environmental changes and competition between species gradually lead to the extinction of species lines.

However, as a result of research, it became clear that the Cretaceous period (from 145 to 66 million years ago) ended with an extraordinary wave of extinctions. In a short period of time, a large number of species have gone extinct around the world. The discovery of the 180km-wide Chicculub asteroid impact crater on Mexico’s Yucatan Peninsula suggests sudden extinction of dinosaurs and other species caused by the impact. But other studies argue that a long, slow decline in dinosaur diversity contributed to their extinction.

“Putting the story together is difficult. It’s not just that dinosaur fossils are so rare; The fossil record is also patchy.” flashes Nicolas R. Longrich. And for good reason: most research so far has been carried out in the northern hemisphere (USA, Canada or Mongolia), while research on dinosaurs from the southern continents has been rare, in part due to the inaccessible topography from tropical regions.

Additionally, the table may be biased given that Africa, a huge continent, was likely home to many more species of dinosaurs than North America, especially Morocco, where “the most dangerous region in the history of the Earth “.

Except that on the vast continent there are few terrestrial rocks from the end of the Cretaceous period. “This is because the level of volcanic activity has caused sea levels to rise, submerging much of Africa under shallow waters. Dinosaurs, being terrestrial, are rarely found in sea cliffs. But rarely does not mean never. Study enough marine fossils and eventually you’ll find a dinosaur. warns Nicholas R. Longrich.

And it is in Morocco, where the largest phosphate deposits (in other words, ancient seabeds) dating back to the last million years of the age of the dinosaurs are located, that crucial clues emerge: they are full of ribs and fish scales, shark teeth and large numbers of marine reptiles – mosasaurs, plesiosaurs, marine turtles. And also dinosaur bones.

Read about it : In the footsteps of a Spinosaurus in the Moroccan desert.

Nicholas R. Longrich wonders about the reasons for the presence of these dinosaur bones in the marine sediments of Morocco: “Dinosaurs may have sailed to the islands in search of food, as deer and elephants do today, and some may have drowned. Other dinosaurs may have been washed out to sea by floods or storms, or drowned in rivers that carried them out to sea. Still others may have died on shore before being evacuated at high tide.” However, a series of incredible events brought the dinosaurs to the ocean.

“So, by studying the seabed and working for many years, we have gradually built up a picture of Africa’s last dinosaurs, bone by bone,” – says the paleontologist.

Fossils of several species of Abelisaurus have been discovered, indicating dinosaur diversity in Morocco at the end of the Cretaceous. Photo: Andrey Atuchin/University of Bath.

Among Africa’s last dinosaurs were the titanosaur sauropods, long-necked herbivores the size of elephants. The niche of herbivores was occupied by horse-sized duck-billed dinosaurs.

Read about it : For the first time in Africa, the remains of duck-billed dinosaurs were discovered in Khuribga.

“But the predators are especially interesting. Situated at the top of the food chain, they tell us a lot about the ecosystem. And African carnivorous dinosaurs were diverse, including a variety of herbivores, and in large numbers.” adds the specialist.

According to him, the main predator was a ten-meter animal called Chenanisaurus barbaricus. “So far, Chenanisaurus is only known from its jaws, but this tells us that it was part of the Abelisauridae, a strange family of predators found in South America, India, Madagascar and Europe, while the north was dominated by tyrannosaurs. Abelisaurs had short, bulldog-like snouts and sometimes horns, and strange, stubby arms that made tyrannosaurs’ arms look massive in comparison. explains Nicholas R. Longrich.

What’s new is that fossils of two new abelisaurs have turned up in Morocco.

Read about it : Fossils of ‘primitive relatives of Tyrannosaurus rex’ discovered in Morocco

One of them was identified from the tibia. “It was smaller than Chenanisaurus, about five meters long – small by dinosaur standards, but large by modern predator standards. Oddly enough, it resembles the abelisaurs found in South America. It is possible that this marks an ancient land connection that existed between the continents 100 million years ago. Or the abelisaurs could have swam across the narrow sea route separating the continents.”

“Another bone comes from the foot of an even smaller abelisaurid, only three meters long. Similar small abelisaurids are present in Europe and this may be related to them.” promoted by paleontologist.

Dinosaurs of the Upper Maastrichtian of Morocco. Source: Nick Longrich

More dinosaur fossils and new species have been discovered in recent months. “We’re still analyzing these fossils, so we can’t say anything at the moment, but finding so many species in just a few fossils tells us that we’re collecting samples of a very diverse fauna.” – the researcher concludes.

And add this “Although fossils from the Great Plains of North America may document a decline in dinosaur diversity, this may be a local rather than a global phenomenon. It is possible that global cooling during the Last Cretaceous hit higher latitudes hard, reducing diversity. But the African dinosaur fauna suggests that at lower latitudes dinosaurs flourished and even diversified. If this is true, then this means that dinosaurs were exterminated at the peak of their development.”

Read about it : Thalassotitan, a new marine megapredator discovered in Morocco.

Additionally, Nicholas R. Longrich believes that the last dinosaurs of Africa, especially various carnivorous dinosaurs, flourished shortly before their sudden extinction: “Over 100 million years, they have evolved and diversified, creating an amazing diversity of species: predators, herbivores, aquatic species, even flying forms, birds. Then, in one cataclysmic moment, everything was destroyed during months of darkness caused by dust and the aftermath of an asteroid impact in Mexico.” Of the entire cataclysm, only half a dozen species of birds survived…

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